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69 lines
1.8 KiB
C
69 lines
1.8 KiB
C
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/* Copyright (C) 1994 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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The GNU C Library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Library General Public License as
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published by the Free Software Foundation; either version 2 of the
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License, or (at your option) any later version.
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The GNU C Library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Library General Public License for more details.
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You should have received a copy of the GNU Library General Public
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License along with the GNU C Library; see the file COPYING.LIB. If
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not, write to the Free Software Foundation, Inc., 675 Mass Ave,
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Cambridge, MA 02139, USA. */
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#include <sys/types.h>
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#include <unistd.h>
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#include <fcntl.h>
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#include <errno.h>
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/* lockf is a simplified interface to fcntl's locking facilities. */
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int
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lockf (int fd, int cmd, off_t len)
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{
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struct flock fl;
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switch (cmd)
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{
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case F_TEST:
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/* Test the lock: return 0 if FD is unlocked or locked by this process;
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return -1, set errno to EACCES, if another process holds the lock. */
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if (fcntl (fd, F_GETLK, &fl) < 0)
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return -1;
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if (fl.l_type == F_UNLCK || fl.l_pid == getpid ())
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return 0;
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errno = EACCES;
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return -1;
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case F_ULOCK:
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fl.l_type = F_UNLCK;
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cmd = F_SETLK;
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break;
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case F_LOCK:
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fl.l_type = F_WRLCK;
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cmd = F_SETLKW;
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break;
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case F_TLOCK:
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fl.l_type = F_WRLCK;
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cmd = F_SETLK;
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break;
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default:
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errno = EINVAL;
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return -1;
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}
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/* lockf is always relative to the current file position. */
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fl.l_whence = SEEK_CUR;
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fl.l_start = 0;
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fl.l_len = len;
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return fcntl (fd, cmd, &fl);
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}
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